Centromere: Absence of DNA Replication during Chromatid Separation in Human Fibroblasts

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Science  16 Dec 1966:
Vol. 154, Issue 3755, pp. 1463-1464
DOI: 10.1126/science.154.3755.1463


Cultures of human fibroblasts were labeled briefly with tritiated thymidine and fixed; autoradiographs were made and exposed for 3½ months. No labeling was noted over the centromere of metaphase or anaphase chromosomes. The technique was sensitive to replication at the centromere of a DNA helix only 2.5 microns long, considerably shorter than the estimated length of a replicon in humans. This suggests that chromatid separation during mitosis is not associated with delayed replication of a short segment of chromosomal DNA.